A fotopiroelektromos effektus (PPE) szinte még teljesen ismeretlen hazánkban, pedig a módszer alkalmazásával különböző élelmiszerek hőtani tulajdonságai közvetlenül meghatározhatók. Az élelmiszerek termikus tulajdonságainak megismerése fontos technológiai újításokat eredményezhet az élelmiszeripar területén. Mindezek mellett az élelmiszerhamisítások leleplezésében is fontos szerepet játszhat az elkövetkező időkben. A fotopiroelektromos vizsgálatok nagy előnye a hozzá hasonló mérési módszerekkel szemben a mérések viszonylagos egyszerűsége, gyorsasága és költséghatékonysága. A fotopiroelektromos módszernek többféle elrendezése ismert. Ilyenek a sztenderd és az inverz fotopiroelektromos módszer. A két elrendezést a minta és a szenzor elhelyezése különbözteti meg egymástól.
Mindkét konfiguráció esetében szaggatott fénynyalábot alkalmaznak.
Ez a szaggatott fény abszorbeálódik – inverz elrendezésnél a piroelektromos fólián, míg sztenderd elrendezésnél a mintán – és hőhullámokká alakul. A bekövetkező hőmérsékletváltozást a piroelektromos fólia detektálja. Ezáltal létrejön a fotopiroelektromos jel, amelyből relatív módszerrel a minta effuzivitás értéke közvetlenül kiszámítható.
Kísérleteinkben különböző élelmiszerek hőeffuzivitását határoztuk meg, amelyhez az inverz fotopiroelektromos elrendezést alkalmaztuk.
Ennek a módszernek előnye, hogy nem kell ismerni a mérendő minta vastagságát, ami megkönnyíti a mérés menetét. Első lépésként egy
laboratóriumi körülmények között működő rendszert kellett összeállítani, amivel a tervezett méréseket el tudtuk végezni.
A mérőrendszer összeállítását követően számos élelmiszer effuzivitás értékét mértük meg és a kapott értékeket összehasonlítottuk az irodalomban megtalálható értékekkel. Ezután az irodalomban eddig ismeretlen effuzivitású élelmiszerek effuzivitás értékét határoztuk meg.
Méréseink következő lépéseként különböző élelmiszerek effuzivitását határoztuk meg azok zsírtartalmának függvényében. A kapott eredmények jól mutatják, hogy az adott élelmiszer zsírtartalmának növelése lineárisan csökkenti az élelmiszer effuzivitás értékét és lehetőséget nyújt élelmiszerek zsírtartalmának meghatározására.
Méréseink kiterjedtek különböző élelmiszer manipulációk kimutatására is. Bor és méz minták esetében a leggyakrabban használt manipulációs technikákat (glicerin valamint izocukor hozzáadását) sikerült kimutatni. A kvalitatív eredmény mellett, analitikai összefüggéseket határoztunk meg a hamisítás mértékének kimutatására.
A különböző madárfajok tojásainak és tojás alkotóinak effuzivitás értékeit és meghatároztuk, valamint statisztikai módszerrel bebizonyítottuk ezek szignifikáns különbségét. Továbbá tojásporok rehidratálás mértékére tettünk javaslatokat a minták effuzivitás értékének egyezése alapján. A kapott eredményekből kiindulva az ipari alkalmazás megváltoztatása is javasolható. Mivel az effuzivitás értéke más módszerekkel közvetlenül nem mérhető ezért a PPE
módszer megjelenése előtt csak az adott fizikai paraméterek ismeretéből való számításos úton lehetett meghatározni. Alkalmazva az IPPE módszert, azaz közvetlenül határoztuk meg az effuzivitást, ami lehetőséget adott a számított eredményekkel való összehasonlításra. Az eredmények 10%-nál kisebb eltérést mutattak.
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Táblázatok és ábrák jegyzéke
Táblázatok
1. táblázat (29. oldal): Vízre, etilén-glikolra és glicerin mért fajlagos hőkapacitás értékek.
2. táblázat (47. oldal): Tojássárgája-, tojásfehérje és teljes tojáspor főbb beltartalmi paraméterei. (Capriovus Kft.
Specifikációja alapján)
3. táblázat (54. oldal): A különböző vízmennyiséggel készített
3. táblázat (54. oldal): A különböző vízmennyiséggel készített